This invention relates to methods of forming electrical components, and more particularly to a method of forming a package having a sealed network of electric circuit elements.
The use of sealed electric network packages has become quite popular for circuit board and similar applications. Such packages are relatively inexpensive, mass produced components that provide numerous alternatives both in the manner in which they can be connected to an external circuit, and in the choice of electrical characterisitcs available. They typically involve a network of circuit elements such as resistors, inductors, or capacitors that are deposited on a substrate and protected from the outside environment by means of a superstrate which is held on by an adhesive. A number of lead wires make electrical connections at various terminal points on the network and extend out from the package to facilitate connection with an external circuit. Selected portions of the sealed network can then be integrated into a circuit board by soldering or otherwise connecting an appropriate combination of lead wires to the board circuit. The packages generally come in one of two configurations: single-in-line (SIP) with a single set of leads protruding from one edge of the package, and double-in-line (DIP) with two sets of lead wires protruding from opposite edges of the package.
While separate clamps could be used to hold the package together, it has generally been found preferable to employ an adhesive to the substrate and superstrate. In addition to producing a smaller package with possible cost savings, adhesives have the advantage of sealing the enclosed network and thereby providing a first barrier against the outer environment. However, the manufacture of network packages with adhesives has not proved to be completely satisfactory, and there are still areas in which further improvements are desirable. For example, the substrate and superstrate have generally been clamped together during all or a substantial portion of the time in which the adhesive is cured. This in turn has lead to a requirement for fairly expensive machine parts such as molds or dies. Such equipment is generally inflexible in the sense that it cannot readily accommodate changes in the dimensions of the network package, necessitating the maintenance of multiple lines of manufacturing apparatus or frequent retooling if a number of different package sizes are produced either concurrently or in succession. Mass production capability may also be limited because each mold or die is occupied for substantially the entire period necessary to cure the adhesive, thereby necessitating the acquisition of additional molds or dies in order to increase the production rate. Care must also be exercised in the design and operation of the equipment to ensure that the substrates and superstrates are not damaged when the package is clamped.